Vane with an axle pin for axial impeller wheels

ABSTRACT

A vane with an axle pin for axial flow fans comprising a number of vanes, each of which being with its axle pin, connected with a screw thread to the vane root, accommodated rotatably in the hub rim of the impeller wheel. Within the hub rim the pins are connected to means for turning the total number of vanes around their axes and the axes of the associated pins during the operation of the wheel. Outside its screw thread serving for being screwed into the associated vane each pin is provided with a portion having a smaller diameter than the bottom diameter of the screw thread and inside the screw thread it is provided with a portion having a larger diameter than the outer diameter of the screw thread, the bore of the vane being designed as corresponding reamed holes inside and outside a portion having a screw thread corresponding to the screw thread of the pin. Outside the underside of the vane root a fixation ring is provided on the pin and through the vane root a fixation screw is screwed in, the end of which engages a reamed aperture in the fixation ring.

United States Patent 1 Pedersen et a1.

[ VANE WITH AN AXLE PIN FOR AXIAL IMPELLER WHEELS [75] Inventors: BendtOve Pedersen; Ole Jacobsen Bredsted, both of Naestved, Denmark [73]Assignee: Nordisk Ventilator Co. A/S,

Naestved, Denmark 22 Filed: Jan. 22, 1974 21 App]. NO.Z 435,627

[30] Foreign Application Priority Data Jan. 22, 1973 Denmark 340/73 [52]US. Cl 416/168; 416/164 [51] Int. Cl. F04D 29/36 [58] Field of Search416/163-168, 416/207 [56] References Cited UNITED STATES PATENTS1,497,723 6/1924 l-Iuguenin 416/168 A X 2,054,810 9/1936 Gaba 416/165 X2,844,303 7/1958 Kristiansen 416/164 3,085,631 4/1963 Dagrell 416/168 XI FOREIGN PATENTS OR APPLICATIONS 1,377,164 9/1964 France 416/1681,403,498 7/1969 Germany 416/168 707,844 4/1954 UnitedKingdom 416/168 1Sept. 23, 1975 823.526 11/1959 United Kingdom 416/168 PrimaryExaminer-Everette A. Powell, Jr. Attorney, Agent, or FirmSughrue,Rothwell, Mion, Zinn & Macpeak 5 7] 1 ABSTRACT A vane with an axle pinfor axial flow fans comprising a number of vanes, each of which beingwith its axle pin, connected with a screw thread to the vane root,accommodated rotatably in the hub rim of the impeller wheel. Within thehub rim the pins are connected to means for turning the total number ofvanes around their axes and the axes of the associated pins during theoperation of the wheel. Outside its screw thread serving for beingscrewed into the associated vane each pin is provided with a portionhaving a smaller diameter than the bottom diameter of the screw threadand inside the screw thread it is provided with a portion having alarger diameter than the outer diameter of the screw thread, the bore ofthe vane being designed as corresponding reamed holes inside and outsidea portion having a screw thread corresponding to the screw thread of thepin. Outside the underside of the vane root a fixation ring is providedon the pin and through the vane root a fixation screw is screwed in, theend of which engages a reamed aperture in the fixation ring.

1 Claim, 2 Drawing Figures US Patent Sept. 23,1975 Sheet 2 of2 3,907,460

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VANE WITH AN AXLE PIN FOR AXIAL IMPELLER WHEELS The invention relates toa vane with an axle pin for axial flow fans comprising a number ofvanes, each of which with its pin, connected with a screw thread to thevane root, is accommodated rotatably in the hub rim of the impellerwheel and where within the hub rim the pins are connected to means forturning the total number of vanes around their axes and the axes of theassociated pins during the operation of the wheel.

In such axial flow impeller wheels, particularly those having largediameters, the vanes are subjected to extremely great centrifugalforces. It may sometimes be a question of forces of up to 50 tons pervane or more.

Due to correspondingly great axial bearing pressures and the very hightorque exerted on the vane during the operation, very great demands areput to the attachment of the pin in the vane. As a rule it will be outof the question to manufacture vane and pin in one piece, particularlywhen the vane is manufactured of cast material. Moreover it will, inparticular when the fan is intended for operating in dust-containinggases which may cause a considerable wear of the vanes, be of importancethat it is possible to exchange the vanes from the outside, that is tosay without it being necessary to perform any operations in the interiorof the hub. It is an additional requirement that the means for securingthe attachment do not take up too much space, since there is only arelatively small space at disposal. Furthermore, they must not give riseto any essential weakening of the material of the vane root. 7

From British patent specification No. 627 258 an impeller wheel is knownin which each vane is secured to a wheel rim by the vane root, whichextends through a bore with a bearing in the wheel rim, being providedwith a bore having a screw thread extending to the bottom of the bore,into which screw thread a shaft pin has been screwed, the said shaft'pin being at its opposite end via an end piece with a bearing connectedto the hub. In the case of such a construction, the screw thread in thebore of the vane foot will, besides being subjected to the centrifugalforces acting in the axial direction, also be subjected to considerableradial forces, and this makes it necessary, in particular in the case offast-running axial flow impeller wheels having large diameters, to havethe screw thread designed as a very tight-fitting thread. Such atight-fitting screw thread will, however, besides increased costs ofmanu facture, also, as is mentioned in the following, cause that thescrewing in of the pin is made difficult and that the risk of damage tothe screw thread during this screwing-in operation is increased.

The problems mentioned above are solved in a particularly satisfactoryway according to the invention by each pin outside its screw threadintended for being vane, the end of which fixation screw engages areamed or fitting opening in the fixation ring.

The construction of the pin as fitting pins inside and outside the screwthread in connection with the corresponding reamed or fitting bores inthe vane serves for absorbing radial forces, so that the screw thread isintended for absorbing only the centrifugal force directed in the axialdirection. Since consequently the screw thread is not intended forabsorbing the radial forces it is unnecessary to design this thread as atight-fitting thread, and this is advantageous, since the screwing in ofthe pin would be made considerably more difficult and there would be agreat risk of the thread seizing during the screwing-in operation sothat the thread was damaged in particular the screw thread in the vanewhen the latter is manufactured of light-weight metal, and if the screwthread is damaged the vane has to be discarded, there being no practicalpossibility of boring out the thread and cutting a new thread having alarger diameter, since in this case it would be necessary to perform acorresponding boring out of all vanes and substitute all pins by pinshaving a heavier thread. The torsional forces occurring are duringperiods of standstill absorbed by the fixation screw through thefixation ring, and as this screw passes through the vane root in theaxial direction, the hole in the vane root can be bored in a place whereit does not cause any perceptible weakening of the material and,moreover, at such a distance from the axis that the reaction exerted bythe screw against the torsion will act on a fairly large diameter sothat a comparatively thin screw may be used. During the operation of thewheel, the very great centrifugal force acting on the vane in the axialdirection of the pin causes that the thread is self-blocking and therebyabsorbs the torsional forces.

The fixation ring may be constructed in one piece with the pin, butsince it has a considerably larger diameter than the remaining part ofthe pin this causes a large waste of material, so that a shrinking-on ofthe fixation ring will be preferable.

In an embodiment of the invention the fixation ring has been shrunk ontothe pin, while its aperture viewed in the direction at right angles toits plane is divided into two circular eccentrical sections, and the pinis provided with an eccentrical part corresponding to one of thesesections.

Usually, a shrinking on of the fixation ring would be supposed to offerthe sufficient security, but the fact that the ring is provided with twoeccentrical sections and the pin with a corresponding eccentrical partoffers a very considerable increase in the security against the fixationring and the pin being turned ever so slightly relative to each other.

Below, the invention will be explained in greater detail with referenceto the drawing in which screwed into the associated vane being providedwith l a portion having a smaller diameter than the bottom diameter ofthe screw thread, and inside the screw thread being provided with aportion having a larger diameter than the outer diameter of the screwthread, and by the bore of the vane being designed as correspondingreamed or fitting holes inside and outside a portion with a screw threadcorresponding to the screw thread of the pin and by a fixation ringbeing provided on the pin outside the underside of the vane root and bya fixation screw being screwed in through the root of the FIG. 1diagrammatically shows part of an axial flow impeller wheel with a fewvanes with the associated pins in an embodiment of the invention andFIG. 2 shows a section on line II-II in FIG. 1, a larger part of thewheel being, however, shown in this illustration.

The hub 2 of the wheel is secured on the wheel shaft 1. The hub is inthis embodiment constructed in one piece with a hub disc 3 and a hub rim4. In the hub rim a number of vanes 5 have been accommodated, each ofwhich comprises an axle pin 6 in an axial bearing 7 secured with a nut 8which at the same time secures an intermediate portion on the pin 6 withan adjustment arm 9 and with two balancing wings 10 which in theirextreme ends are filled with lead 1 1 to achieve the necessarybalancing. Each adjustment arm 9 is by means of a link rod 12 connectedto an adjustment disc 13 which is axially displaceable relative to thewheel, but rotates together with the latter by means of drivers, ofwhich FIG. 2 shows a single driver 14.

The pin 6 is secured to the vane 5 at the root 15 of the vane by meansof a screw thread 16. Outside the screw thread 16 the pin 6 has afitting portion 17 having a smaller diameter than the bottom diameter ofthe screw thread, and inside the screw thread it has a fitting portion18 with a diameter larger than the outer diameter of the screw thread.These fitting portions 17 and 18 fit into corresponding parts of thebore in the vane root 15 inside and outside the screw thread 16.

These fitting portions serve for absorbing the radial forces, and forabsorbing the torsional forces there has on the pin 6 been shrunk on afixation ring 19 which cooperates with a fixation screw 20 which isscrewed down through the vane root 15 with a threaded part 21 and at itsend is provided with a fitting portion 22 for corresponding reamed holesin the vane root l5 and in the fixation ring 19.

As an additional safeguard against a turning of the pin 6 relative tothe vane root 15 the aperture of the fixation ring 19 is, viewed in theaxial direction, designed with two sections which are mutuallyeccentrical, while the pin 6 is provided with two corresponding portions23 and 24 fitting these sections, the portion 23 being eccentricalrelative to the axis of the pin with the same degree of eccentricity asthe two sections in the aperture of the fixation ring 19.

In order to ensure that the fixation screw 20 cannot in the case ofvibrations occurring work loose and thereby be flung out between thevanes, which might destroy the latter completely, the fixation screw 20is secured in the vane root 15 by means ofa locking screw 25 whichengages a turned-down groove 26 in the fixation screw 20 between thethreaded part 21 and the fitting portion 22. Out of regard to themounting this groove 26 has a length which is sufficient for in partletting the fixation screw 20 go quite clear of the fixation ring 19, inpart enabling the fixation screw to be screwed down to the full depthwithout it being necessary to remove the locking screw 25.

In the drawing, the fitting portions 17 and 18 are shown cylindrical,but at any rate one of these portions may be designed so as to beconical.

What is claimed is:

1. In a vane mounting assembly for an axial flow fan having a pluralityof vanes (5) rotatably mounted in a hub rim (4) of an impeller wheel,each vane being mounted in the hub rim by an axle pin (6) having athreaded portion (16) engaging a correspondingly threaded portion in abore in a root portion (15) of each vane, and including means (9, 12,13) connected to each axle pin for simultaneously rotating all of thevanes about the axes of the axle pins, the improvements characterizedby:

a. a first portion (17) of the axle pin between the threaded portion andthe nearest end of the axle pin having a diameter less than the insidediameter of the threaded portion,

b. a second portion (18) of the axle pin between the threaded portionand the farthest end of the axle pin having a diameter greater than theoutside diameter of the threaded portion,

c. the bore in the root portion of each vane including an inner portionhaving a diameter generally corresponding to and for receiving saidfirst portion of the axle pin and an outer portion having a diametergenerally corresponding to and for receiving said second portion of theaxle pin,

(1. a fixing ring (19) rigidly mounted on the axle pin beneath thebottom of the root portion of the vane when the axle pin is threadedthereinto, said ring extending outwardly from the axle pin and having anaperture therethrough, and

e. a locking screw (20) threaded into and extending through a bore inthe root portion of the vane, an end (22) of said screw extending intothe aperture in the fixing ring, whereby the first and second portionsof the axle pin absorb radial forces during the operation of the fan,the threaded portion absorbs centrifugal forces, and the locking screwabsorbs torsional forces.

1. In a vane mounting assembly for an axial flow fan having a pluralityof vanes (5) rotatably mounted in a hub rim (4) of an impeller wheel,each vane being mounted in the hub rim by an axle pin (6) having athreaded portion (16) engaging a correspondingly threaded portion in abore in a root portion (15) of each vane, and including means (9, 12,13) connected to each axle pin for simultaneously rotating all of thevanes about the axes of the axle pins, the improvements characterizedby: a. a first portion (17) of the axle pin between the threaded portionand the nearest end of the axle pin having a diamEter less than theinside diameter of the threaded portion, b. a second portion (18) of theaxle pin between the threaded portion and the farthest end of the axlepin having a diameter greater than the outside diameter of the threadedportion, c. the bore in the root portion of each vane including an innerportion having a diameter generally corresponding to and for receivingsaid first portion of the axle pin and an outer portion having adiameter generally corresponding to and for receiving said secondportion of the axle pin, d. a fixing ring (19) rigidly mounted on theaxle pin beneath the bottom of the root portion of the vane when theaxle pin is threaded thereinto, said ring extending outwardly from theaxle pin and having an aperture therethrough, and e. a locking screw(20) threaded into and extending through a bore in the root portion ofthe vane, an end (22) of said screw extending into the aperture in thefixing ring, whereby the first and second portions of the axle pinabsorb radial forces during the operation of the fan, the threadedportion absorbs centrifugal forces, and the locking screw absorbstorsional forces.